<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2015, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT    MIT License
 * @link    http://codeigniter.com
 * @since    Version 3.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * PDO SQLSRV Database Adapter Class
 *
 * Note: _DB is an extender class that the app controller
 * creates dynamically based on whether the query builder
 * class is being used or not.
 *
 * @package        CodeIgniter
 * @subpackage    Drivers
 * @category    Database
 * @author        EllisLab Dev Team
 * @link        http://codeigniter.com/user_guide/database/
 */
class CI_DB_pdo_sqlsrv_driver extends CI_DB_pdo_driver {

    /**
     * Sub-driver
     *
     * @var    string
     */
    public $subdriver = 'sqlsrv';

    // --------------------------------------------------------------------

    /**
     * ORDER BY random keyword
     *
     * @var    array
     */
    protected $_random_keyword = array('NEWID()', 'RAND(%d)');

    /**
     * Quoted identifier flag
     *
     * Whether to use SQL-92 standard quoted identifier
     * (double quotes) or brackets for identifier escaping.
     *
     * @var    bool
     */
    protected $_quoted_identifier;

    // --------------------------------------------------------------------

    /**
     * Class constructor
     *
     * Builds the DSN if not already set.
     *
     * @param    array    $params
     * @return    void
     */
    public function __construct($params)
    {
        parent::__construct($params);

        if (empty($this->dsn))
        {
            $this->dsn = 'sqlsrv:Server='.(empty($this->hostname) ? '127.0.0.1' : $this->hostname);

            empty($this->port) OR $this->dsn .= ','.$this->port;
            empty($this->database) OR $this->dsn .= ';Database='.$this->database;

            // Some custom options

            if (isset($this->QuotedId))
            {
                $this->dsn .= ';QuotedId='.$this->QuotedId;
                $this->_quoted_identifier = (bool) $this->QuotedId;
            }

            if (isset($this->ConnectionPooling))
            {
                $this->dsn .= ';ConnectionPooling='.$this->ConnectionPooling;
            }

            if ($this->encrypt === TRUE)
            {
                $this->dsn .= ';Encrypt=1';
            }

            if (isset($this->TraceOn))
            {
                $this->dsn .= ';TraceOn='.$this->TraceOn;
            }

            if (isset($this->TrustServerCertificate))
            {
                $this->dsn .= ';TrustServerCertificate='.$this->TrustServerCertificate;
            }

            empty($this->APP) OR $this->dsn .= ';APP='.$this->APP;
            empty($this->Failover_Partner) OR $this->dsn .= ';Failover_Partner='.$this->Failover_Partner;
            empty($this->LoginTimeout) OR $this->dsn .= ';LoginTimeout='.$this->LoginTimeout;
            empty($this->MultipleActiveResultSets) OR $this->dsn .= ';MultipleActiveResultSets='.$this->MultipleActiveResultSets;
            empty($this->TraceFile) OR $this->dsn .= ';TraceFile='.$this->TraceFile;
            empty($this->WSID) OR $this->dsn .= ';WSID='.$this->WSID;
        }
        elseif (preg_match('/QuotedId=(0|1)/', $this->dsn, $match))
        {
            $this->_quoted_identifier = (bool) $match[1];
        }
    }

    // --------------------------------------------------------------------

    /**
     * Database connection
     *
     * @param    bool    $persistent
     * @return    object
     */
    public function db_connect($persistent = FALSE)
    {
        if ( ! empty($this->char_set) && preg_match('/utf[^8]*8/i', $this->char_set))
        {
            $this->options[PDO::SQLSRV_ENCODING_UTF8] = 1;
        }

        $this->conn_id = parent::db_connect($persistent);

        if ( ! is_object($this->conn_id) OR is_bool($this->_quoted_identifier))
        {
            return $this->conn_id;
        }

        // Determine how identifiers are escaped
        $query = $this->query('SELECT CASE WHEN (@@OPTIONS | 256) = @@OPTIONS THEN 1 ELSE 0 END AS qi');
        $query = $query->row_array();
        $this->_quoted_identifier = empty($query) ? FALSE : (bool) $query['qi'];
        $this->_escape_char = ($this->_quoted_identifier) ? '"' : array('[', ']');

        return $this->conn_id;
    }

    // --------------------------------------------------------------------

    /**
     * Show table query
     *
     * Generates a platform-specific query string so that the table names can be fetched
     *
     * @param    bool    $prefix_limit
     * @return    string
     */
    protected function _list_tables($prefix_limit = FALSE)
    {
        $sql = 'SELECT '.$this->escape_identifiers('name')
            .' FROM '.$this->escape_identifiers('sysobjects')
            .' WHERE '.$this->escape_identifiers('type')." = 'U'";

        if ($prefix_limit === TRUE && $this->dbprefix !== '')
        {
            $sql .= ' AND '.$this->escape_identifiers('name')." LIKE '".$this->escape_like_str($this->dbprefix)."%' "
                .sprintf($this->_like_escape_str, $this->_like_escape_chr);
        }

        return $sql.' ORDER BY '.$this->escape_identifiers('name');
    }

    // --------------------------------------------------------------------

    /**
     * Show column query
     *
     * Generates a platform-specific query string so that the column names can be fetched
     *
     * @param    string    $table
     * @return    string
     */
    protected function _list_columns($table = '')
    {
        return 'SELECT COLUMN_NAME
            FROM INFORMATION_SCHEMA.Columns
            WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));
    }

    // --------------------------------------------------------------------

    /**
     * Returns an object with field data
     *
     * @param    string    $table
     * @return    array
     */
    public function field_data($table)
    {
        $sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT
            FROM INFORMATION_SCHEMA.Columns
            WHERE UPPER(TABLE_NAME) = '.$this->escape(strtoupper($table));

        if (($query = $this->query($sql)) === FALSE)
        {
            return FALSE;
        }
        $query = $query->result_object();

        $retval = array();
        for ($i = 0, $c = count($query); $i < $c; $i++)
        {
            $retval[$i]            = new stdClass();
            $retval[$i]->name        = $query[$i]->COLUMN_NAME;
            $retval[$i]->type        = $query[$i]->DATA_TYPE;
            $retval[$i]->max_length        = ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;
            $retval[$i]->default        = $query[$i]->COLUMN_DEFAULT;
        }

        return $retval;
    }

    // --------------------------------------------------------------------

    /**
     * Update statement
     *
     * Generates a platform-specific update string from the supplied data
     *
     * @param    string    $table
     * @param    array    $values
     * @return    string
     */
    protected function _update($table, $values)
    {
        $this->qb_limit = FALSE;
        $this->qb_orderby = array();
        return parent::_update($table, $values);
    }

    // --------------------------------------------------------------------

    /**
     * Delete statement
     *
     * Generates a platform-specific delete string from the supplied data
     *
     * @param    string    $table
     * @return    string
     */
    protected function _delete($table)
    {
        if ($this->qb_limit)
        {
            return 'WITH ci_delete AS (SELECT TOP '.$this->qb_limit.' * FROM '.$table.$this->_compile_wh('qb_where').') DELETE FROM ci_delete';
        }

        return parent::_delete($table);
    }

    // --------------------------------------------------------------------

    /**
     * LIMIT
     *
     * Generates a platform-specific LIMIT clause
     *
     * @param    string    $sql    SQL Query
     * @return    string
     */
    protected function _limit($sql)
    {
        // As of SQL Server 2012 (11.0.*) OFFSET is supported
        if (version_compare($this->version(), '11', '>='))
        {
            // SQL Server OFFSET-FETCH can be used only with the ORDER BY clause
            empty($this->qb_orderby) && $sql .= ' ORDER BY 1';

            return $sql.' OFFSET '.(int) $this->qb_offset.' ROWS FETCH NEXT '.$this->qb_limit.' ROWS ONLY';
        }

        $limit = $this->qb_offset + $this->qb_limit;

        // An ORDER BY clause is required for ROW_NUMBER() to work
        if ($this->qb_offset && ! empty($this->qb_orderby))
        {
            $orderby = $this->_compile_order_by();

            // We have to strip the ORDER BY clause
            $sql = trim(substr($sql, 0, strrpos($sql, $orderby)));

            // Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results
            if (count($this->qb_select) === 0)
            {
                $select = '*'; // Inevitable
            }
            else
            {
                // Use only field names and their aliases, everything else is out of our scope.
                $select = array();
                $field_regexp = ($this->_quoted_identifier)
                    ? '("[^\"]+")' : '(\[[^\]]+\])';
                for ($i = 0, $c = count($this->qb_select); $i < $c; $i++)
                {
                    $select[] = preg_match('/(?:\s|\.)'.$field_regexp.'$/i', $this->qb_select[$i], $m)
                        ? $m[1] : $this->qb_select[$i];
                }
                $select = implode(', ', $select);
            }

            return 'SELECT '.$select." FROM (\n\n"
                .preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER('.trim($orderby).') AS '.$this->escape_identifiers('CI_rownum').', ', $sql)
                ."\n\n) ".$this->escape_identifiers('CI_subquery')
                ."\nWHERE ".$this->escape_identifiers('CI_rownum').' BETWEEN '.($this->qb_offset + 1).' AND '.$limit;
        }

        return preg_replace('/(^\SELECT (DISTINCT)?)/i','\\1 TOP '.$limit.' ', $sql);
    }

    // --------------------------------------------------------------------

    /**
     * Insert batch statement
     *
     * Generates a platform-specific insert string from the supplied data.
     *
     * @param    string    $table    Table name
     * @param    array    $keys    INSERT keys
     * @param    array    $values    INSERT values
     * @return    string|bool
     */
    protected function _insert_batch($table, $keys, $values)
    {
        // Multiple-value inserts are only supported as of SQL Server 2008
        if (version_compare($this->version(), '10', '>='))
        {
            return parent::_insert_batch($table, $keys, $values);
        }

        return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
    }

}
